A monoterpene, unique component of thyme honeys, induces apoptosis in prostate cancer cells via inhibition of NF-κB activity and IL-6 secretion.

We have previously demonstrated that Greek thyme honey inhibits significantly the cell viability of human prostate cancer cells. Herein, 15 thyme honey samples from several regions of Greece were submitted to phytochemical analysis for the isolation, identification and determination (through modern spectral means) of the unique thyme honey monoterpene, the compound trihydroxy ketone E-4-(1,2,4-trihydroxy-2,6,6-trimethylcyclohexyl)-but-3-en-2-one. We investigated the anti-growth and apoptotic effects of the trihydroxy ketone on PC-3 human androgen independent prostate cancer cells using MTT assay and Annexin V-FITC respectively. The molecular pathways involved to such effects were further examined by evaluating its ability to inhibit (a) the NF-κB phosphorylation (S536), (b) JNK and Akt phosphorylation (Thr183/Tyr185 and S473 respectively) and (c) IL-6 production, using ELISA method. The anti-microbial effects of the trihydroxy ketone against a panel of nine pathogenic bacteria and three fungi were also assessed. The trihydroxy ketone exerted significant apoptotic activity in PC-3 prostate cancer cells at 100 µM, while it inhibited NF-κB phosphorylation and IL-6 secretion at a concentration range 10(-6)-10(-4)M. Akt and JNK signaling were not found to participate in this process. The trihydroxy ketone exerted significant anti-microbial profile against many human pathogenic bacteria and fungi (MIC values ranged from 0.04 to 0.57 mg/ml). Conclusively, the Greek thyme honey-derived monoterpene exerted significant apoptotic activity in PC-3 cells, mediated, at least in part, through reduction of NF-κB activity and IL-6 secretion and may play a key role in the anti-growth effect of thyme honey on prostate cancer cells.

Fatty acids derived from royal jelly are modulators of estrogen receptor functions.

Royal jelly (RJ) excreted by honeybees and used as a nutritional and medicinal agent has estrogen-like effects, yet the compounds mediating these effects remain unidentified. The possible effects of three RJ fatty acids (FAs) (10-hydroxy-2-decenoic-10H2DA, 3,10-dihydroxydecanoic-3,10DDA, sebacic acid-SA) on estrogen signaling was investigated in various cellular systems. In MCF-7 cells, FAs, in absence of estradiol (E(2)), modulated the estrogen receptor (ER) recruitment to the pS2 promoter and pS2 mRNA levels via only ERß but not ERα, while in presence of E(2) FAs modulated both ERß and ERα. Moreover, in presence of FAs, the E(2)-induced recruitment of the EAB1 co-activator peptide to ERα is masked and the E(2)-induced estrogen response element (ERE)-mediated transactivation is inhibited. In HeLa cells, in absence of E(2), FAs inhibited the ERE-mediated transactivation by ERß but not ERα, while in presence of E(2), FAs inhibited ERE-activity by both ERß and ERα. Molecular modeling revealed favorable binding of FAs to ERα at the co-activator-binding site, while binding assays showed that FAs did not bind to the ligand-binding pocket of ERα or ERß. In KS483 osteoblasts, FAs, like E(2), induced mineralization via an ER-dependent way. Our data propose a possible molecular mechanism for the estrogenic activities of RJ's components which, although structurally entirely different from E(2), mediate estrogen signaling, at least in part, by modulating the recruitment of ERα, ERß and co-activators to target genes.

Acteoside and martynoside exhibit estrogenic/antiestrogenic properties.

Acteoside and martynoside are plant phenylpropanoid glycosides exhibiting anticancer, cytotoxic and antimetastatic activities. We investigated their potential to activate estrogen receptor isoforms ERalpha and ERbeta in HeLa cells transfected with an estrogen response element (ERE)-driven luciferase (Luc) reporter gene and an ERalpha or ERbeta expression vector. Their estrogenic/antiestrogenic effects were also assessed in breast cancer cells (MCF7), endometrial cancer cells (Ishikawa) and osteoblasts (KS483), by measuring IGFBP3 levels, cell viability and number of mineralized nodules, respectively, seeking for a natural selective estrogen receptor modulator (SERM). Acteoside and martynoside antagonized both ERalpha and ERbeta (p<0.001), whereas they reversed the effect of E(2) mainly via ERalpha (p<0.001). Martynoside was a potent antiestrogen in MCF-7 cells, increasing, like ICI182780, IGFBP3 levels via the ER-pathway. In osteoblasts, martynoside induced nodule mineralization, which was abolished by ICI182780, implicating an ER-mediated mechanism. Furthermore, its antiproliferative effect on endometrial cells suggests that martynoside may be an important natural SERM. Acteoside was an antiestrogen in breast cancer cells and osteoblasts, without any effect on endometrial cells. Our study suggests that the nature is rich in selective ERalpha and ERbeta ligands, the discovery of which may lead to the development of novel neutraceutical agents.

Evaluation of estrogenic/antiestrogenic activity of ellagic acid via the estrogen receptor subtypes ERalpha and ERbeta.

Ellagic acid is a plant-derived polyphenol, possessing antioxidant, antiproliferative, and antiatherogenic properties. Whether this compound has estrogenic/antiestrogenic activity, however, remains largely unknown. To answer this question, we first investigated the ability of ellagic acid to influence the activity of the estrogen receptor subtypes ERalpha and ERbeta in HeLa cells. Cells co-transfected with an estrogen response element (ERE)-driven luciferase (Luc) reporter gene and an ERalpha- or ERbeta-expression vector were exposed to graded concentrations of ellagic acid. At low concentrations (10(-7) to 10(-9) M), this compound displayed a small but significant estrogenic activity via ERalpha, whereas it was a complete estrogen antagonist via ERbeta. Further evaluation revealed that ellagic acid was a potent antiestrogen in MCF-7 breast cancer-derived cells, increasing, like the pure estrogen antagonist ICI182780, IGFBP-3 levels. Moreover, ellagic acid induced nodule mineralization in an osteoblastic cell line (KS483), an effect that was abolished by the estrogen antagonist. Endometrium-derived epithelial cells (Ishikawa) showed no response to the natural compound by using a cell viability assay (MTT). These findings suggest that ellagic acid may be a natural selective estrogen receptor modulator (SERM).